1. Field of the Invention
This invention relates to lighting devices and systems, and in particular, it relates to devices for generating high brightness multicolor light using wavelength conversion.
2. Description of the Related Art
Wavelength conversion methods that use excitation light produced by solid-state light source such as laser diodes (LDs) or light emitting diodes (LEDs) and wavelength conversion materials such as phosphors or quantum dots can produce high brightness light at wavelengths different from the wavelength of the excitation light. In conventional devices, excitation light impinges on a wavelength conversion material, which absorbs the excitation light and emits light at a wavelength higher than the wavelength of the excitation light. To generate light of different colors, different wavelength conversion materials are typically employed. In a projection system described in commonly owned International Patent Application Publication No. WO 2006/102846 A1 published Oct. 5, 2006, three LED light sources are used to generate red, green and blue light, respectively (see FIG. 15 therein). The light of different colors are directed to a dichroic cross-prism which combine the light beams and direct them to a light modulator, which may be a MEMS (micro electronic mechanical system) device or a liquid crystal device (LCD or LCoS). The LED light sources and the light modulator are controlled in a synchronized manner by a signal processor to produce an image.
In some conventional multicolor illumination devices, a white light source (such as a high pressure mercury lamp) is used in conjunction with a color wheel to generate color lights with controlled time sequences. The color wheel, which is disposed in front of the white light source, is made of multiple color filters each transmitting light of a particular color.